US20190363516A1 - Optical waveguide structure - Google Patents
Optical waveguide structure Download PDFInfo
- Publication number
- US20190363516A1 US20190363516A1 US16/532,696 US201916532696A US2019363516A1 US 20190363516 A1 US20190363516 A1 US 20190363516A1 US 201916532696 A US201916532696 A US 201916532696A US 2019363516 A1 US2019363516 A1 US 2019363516A1
- Authority
- US
- United States
- Prior art keywords
- layer
- optical waveguide
- mesa
- waveguide structure
- optical
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/227—Buried mesa structure ; Striped active layer
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/122—Basic optical elements, e.g. light-guiding paths
- G02B6/124—Geodesic lenses or integrated gratings
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/0607—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature
- H01S5/0612—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying physical parameters other than the potential of the electrodes, e.g. by an electric or magnetic field, mechanical deformation, pressure, light, temperature controlled by temperature
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/0625—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in multi-section lasers
- H01S5/06255—Controlling the frequency of the radiation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/06—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium
- H01S5/062—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes
- H01S5/0625—Arrangements for controlling the laser output parameters, e.g. by operating on the active medium by varying the potential of the electrodes in multi-section lasers
- H01S5/06255—Controlling the frequency of the radiation
- H01S5/06256—Controlling the frequency of the radiation with DBR-structure
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1003—Waveguide having a modified shape along the axis, e.g. branched, curved, tapered, voids
- H01S5/1007—Branched waveguides
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
- H01S5/125—Distributed Bragg reflector [DBR] lasers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/14—External cavity lasers
- H01S5/141—External cavity lasers using a wavelength selective device, e.g. a grating or etalon
- H01S5/142—External cavity lasers using a wavelength selective device, e.g. a grating or etalon which comprises an additional resonator
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/02—Structural details or components not essential to laser action
- H01S5/026—Monolithically integrated components, e.g. waveguides, monitoring photo-detectors, drivers
- H01S5/0261—Non-optical elements, e.g. laser driver components, heaters
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1003—Waveguide having a modified shape along the axis, e.g. branched, curved, tapered, voids
- H01S5/1014—Tapered waveguide, e.g. spotsize converter
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/1028—Coupling to elements in the cavity, e.g. coupling to waveguides adjacent the active region, e.g. forward coupled [DFC] structures
- H01S5/1032—Coupling to elements comprising an optical axis that is not aligned with the optical axis of the active region
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/2205—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers
- H01S5/2206—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers based on III-V materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/20—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers
- H01S5/22—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure
- H01S5/2205—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers
- H01S5/2222—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers having special electric properties
- H01S5/2226—Structure or shape of the semiconductor body to guide the optical wave ; Confining structures perpendicular to the optical axis, e.g. index or gain guiding, stripe geometry, broad area lasers, gain tailoring, transverse or lateral reflectors, special cladding structures, MQW barrier reflection layers having a ridge or stripe structure comprising special burying or current confinement layers having special electric properties semiconductors with a specific doping
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/30—Structure or shape of the active region; Materials used for the active region
- H01S5/34—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers
- H01S5/343—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser
- H01S5/3434—Structure or shape of the active region; Materials used for the active region comprising quantum well or superlattice structures, e.g. single quantum well [SQW] lasers, multiple quantum well [MQW] lasers or graded index separate confinement heterostructure [GRINSCH] lasers in AIIIBV compounds, e.g. AlGaAs-laser, InP-based laser with a well layer comprising at least both As and P as V-compounds
Definitions
- the present disclosure relates to an optical waveguide structure.
- a technology for varying the laser emission wavelength is known in which the refractive indexes of an optical guide layer and a diffraction grating layer, which constitute the optical waveguide structure, are varied by heating the optical waveguide structure using a heater (for example, International Patent Publication No. 2016/152274).
- a heater for example, International Patent Publication No. 2016/152274.
- technologies for providing a low thermal conductivity layer or a low thermal conductivity area between the optical guide layer and the substrate have been disclosed in Japanese Laid-open Patent Publication No. 2015-12176, Japanese Patent No. 5303580, and U.S. Pat. No. 8,236,589.
- an optical waveguide structure which includes a lower cladding layer positioned on a substrate; an optical guide layer positioned on the lower cladding layer; an upper cladding layer positioned on the optical guide layer; and a heater positioned on the upper cladding layer.
- the lower cladding layer, the optical guide layer, and the upper cladding layer constitute a mesa structure.
- the optical guide layer has a lower thermal conductivity than the upper cladding layer.
- W wg ⁇ W mesa ⁇ 3 ⁇ W wg is satisfied, wherein W mesa represents a mesa width of the mesa structure, and W wg represents a width of the optical guide layer.
- the optical guide layer occupies one-third or more of the mesa width in a width direction of the mesa structure.
- FIG. 1 is a schematic diagram illustrating a configuration of a wavelength-tunable laser device that includes an optical waveguide structure according to an embodiment
- FIG. 2 is an upper view of a first optical waveguide portion illustrated in FIG. 1 ;
- FIG. 3A is a cross-sectional view along A-A line illustrated in FIG. 2 ;
- FIG. 3B is a cross-sectional view along B-B line illustrated in FIG. 2 ;
- FIG. 3C is a cross-sectional view along C-C line illustrated in FIG. 2 ;
- FIG. 4 is a diagram illustrating the normalized heat resistance in calculation examples 1 and 2 and illustrating the effective refractive index in the calculation example 1;
- FIG. 5 is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the normalized heat resistance in working examples 1 to 3;
- FIG. 6A is a diagram illustrating the normalized heat resistance in calculation examples 1 to 6;
- FIG. 6B is a diagram illustrating the effective refractive index in the calculation example 1 and the calculation examples 3 to 6;
- FIG. 7 is a diagram illustrating a first modification example of the optical waveguide structure
- FIG. 8 is a diagram illustrating a second modification example of the optical waveguide structure
- FIG. 9 is a diagram illustrating a third modification example of the optical waveguide structure.
- FIG. 10 is a diagram illustrating a fourth modification example of the optical waveguide structure.
- FIG. 1 is a schematic diagram illustrating a configuration of a wavelength-tunable laser device that includes an optical waveguide structure according to an embodiment.
- a wavelength-tunable laser device 100 includes a first optical waveguide portion 10 and a second optical waveguide portion 20 that are formed on a common base S.
- the base S is made of the n-type InP, for example.
- an n-side electrode 30 is formed on the underside surface of the base S.
- the n-side electrode 30 is made of AuGeNi, for example; and makes an ohmic contact with the base S.
- the first optical waveguide portion 10 includes a semiconductor mesa portion 12 with an optical waveguide 11 ; includes a p-side electrode 13 ; includes a micro heater 14 made of titanium (Ti); and includes two electrode pads 15 .
- the first optical waveguide portion 10 has a buried structure, and the optical waveguide 11 is formed to extend in the z-direction inside the semiconductor mesa portion 12 .
- the semiconductor mesa portion 12 is configured by layering InP semiconductor layers, and functions as a cladding portion with respect to the optical waveguide 11 .
- FIG. 2 is an upper view of the first optical waveguide portion 10 .
- the first optical waveguide portion 10 includes a first optical waveguide structure portion 10 A, a second optical waveguide structure portion 10 B, a third optical waveguide structure portion 10 C, and two supporting mesa portions 10 D.
- the first optical waveguide structure portion 10 A, the second optical waveguide structure portion 10 B, and the third optical waveguide structure portion 10 C are connected in that order.
- insulating members 17 are disposed in between the pair of the second optical waveguide structure portion 10 B and the third optical waveguide structure portion 10 C and the two supporting mesa portions 10 D.
- the insulating members 17 are made of polyimide, for example.
- the p-side electrode 13 is disposed along the optical waveguide 11 . Meanwhile, in the semiconductor mesa portion 12 , an SiN protective film (described later) is formed, and the p-side electrode 13 makes contact with the semiconductor mesa portion 12 via an opening formed on the SiN protective film.
- the micro heater 14 is disposed on the SiN protective film and along the optical waveguide 11 .
- the electrode pads 15 are disposed on the SiN protective film. The electrode pads 15 are connected to the micro heater 14 via a wiring pattern (not illustrated) provided on the insulating members 17 . Thus, the micro heater 14 receives the supply of electrical current via the electrode pads 15 and consequently gets heated.
- FIG. 3A is a cross-sectional view along A-A line illustrated in FIG. 2
- FIG. 3B is a cross-sectional view along B-B line illustrated in FIG. 2
- FIG. 3C is a cross-sectional view along C-C line illustrated in FIG. 2
- FIG. 3A is illustrated the cross-section of the first optical waveguide structure portion 10 A
- FIG. 3B is illustrated the cross-section of the second optical waveguide structure portion 10 B
- FIG. 3C is illustrated the cross-section of the third optical waveguide structure portion 10 C.
- the semiconductor mesa portion 12 of the first optical waveguide structure portion 10 A includes a lower cladding layer 12 a , which is made of the n-type InP, on an n-type InP substrate constituting the base S.
- a lower cladding layer 12 a On the lower cladding layer 12 a , an active core layer 11 a representing the optical waveguide 11 in the first optical waveguide structure portion 10 A is layered.
- a first upper cladding layer 12 b made of the p-type InP is layered.
- the upper part of the lower cladding layer 12 a along with the active core layer 11 a and the first upper cladding layer 12 b are subjected to etching to form a stripe mesa structure set to have the width (such as 2 ⁇ m) that is suitable in guiding, in the single mode, light in the band of 1.55 ⁇ m.
- the sides of the stripe mesa structure i.e., the right-left direction of the paper sheet
- a p-type semiconductor layer 12 e is layered on the first upper cladding layer 12 b and the buried structure.
- the p-type semiconductor layer 12 e is configured with a second upper cladding layer 12 ea made of the p-type InP, and a contact layer 12 eb that is made of the p-type InGaAs layered on the second upper cladding layer 12 ea and that constitutes the uppermost layer of the semiconductor mesa portion 12 .
- the p-type semiconductor layer 12 e is provided at least from directly above the first upper cladding layer 12 b across the buried structures present on both sides of the stripe mesa structure.
- the first upper cladding layer 12 b and the second upper cladding layer 12 ea function in an integrated manner as the upper cladding layer with respect to the optical waveguide 11 .
- a SiN protective film 16 is formed to cover the semiconductor mesa portion 12 .
- the p-side electrode 13 is made of AuZn, is formed on the contact layer 12 eb , and makes an ohmic contact with the contact layer 12 eb via an opening 16 a formed on the SiN protective film 16 . With such a configuration, current injection becomes possible from the n-side electrode 30 and the p-side electrode 13 to the active core layer 11 a .
- the buried structure itself is a mesa structure.
- the active core layer 11 a includes a multiple quantum well structure configured with alternate layering of a plurality of well layers and a plurality of barrier layers, and includes an upper optical confinement layer and a lower optical confinement layer that sandwich the multiple quantum well structure in the vertical direction.
- the active core layer 11 a emits light in response to current injection.
- the well layers and the barrier layers constituting the multiple quantum well structure of the active core layer 11 a are made of GaInAsP with mutually different compositions.
- the emission wavelength band from the active core layer 11 a is in the band of 1.55 ⁇ m.
- the lower optical confinement layer is made of the n-type GaInAsP.
- the upper optical confinement layer is made of the p-type GaInAsP.
- the bandgap wavelength of the lower and upper optical confinement layers is set to be shorter than the bandgap wavelength of the active core layer 11 a.
- the semiconductor mesa portion 12 of the second optical waveguide structure portion 10 B has the structure formed by substituting an optical guide layer 11 b made of GaInAsP for the active core layer 11 a in the structure illustrated in FIG. 3A and by removing the contact layer 12 eb .
- the optical guide layer 11 b represents the optical waveguide 11 in the second optical waveguide structure portion 10 B.
- the bandgap wavelength of the optical guide layer 11 b is desirably shorter than the bandgap wavelength of the active core layer 11 a and is equal to 1.2 ⁇ m, for example.
- the buried structure itself is a mesa structure having a tapering structure in which the mesa width continually goes on becoming narrower from the first optical waveguide structure portion 10 A toward the third optical waveguide structure portion 10 C.
- the second optical waveguide structure portion 10 B has a mesa width Wm equal to 10 ⁇ m.
- the second optical waveguide structure portion 10 B has a length L equal to 100 ⁇ m, or 120 ⁇ m, or 150 ⁇ m.
- the semiconductor mesa portion 12 of the third optical waveguide structure portion 10 C has a structure formed by substituting an optical guide layer 11 ca , a spacer layer 12 f , and a diffraction grating layer 11 cb for the optical guide layer 11 b and the first upper cladding layer 12 b in the structure illustrated in FIG. 3B .
- the micro heater 14 is disposed on the SiN protective film 16 .
- the optical guide layer 11 ca , the spacer layer 12 f , and the diffraction grating layer 11 cb represent the optical waveguide 11 in the third optical waveguide structure portion 10 C.
- the optical guide layer 11 ca is made of GaInAsP.
- the bandgap wavelength of the optical guide layer 11 ca is desirably shorter than the bandgap wavelength of the active core layer 11 a and is equal to 1.2 ⁇ m, for example.
- the diffraction grating layer 11 cb includes sampled grating that is provided along the optical guide layer 11 ca and provided near and directly above the optical guide layer 11 ca across the spacer layer 12 f made of the p-type InP; and is formed as a diffraction grating layer of the distributed Bragg reflector (DBR) type. That is, the diffraction grating layer 11 cb is positioned on the side of the second upper cladding layer 12 ea with respect to the optical guide layer 11 ca .
- DBR distributed Bragg reflector
- the diffraction grating layer 11 cb has a configuration in which sampled grating is formed in the P-type GaInAsP layer along the z-direction, and the slits in the diffraction grating are buried with InP.
- the grating spacing of the diffraction grating is regular and is sampled, and thus produces a substantially cyclic reflex response with respect to the wavelength.
- the bandgap wavelength of the p-type GaInAsP layer of the diffraction grating layer 11 cb is desirably shorter than the bandgap wavelength of the active core layer 11 a and is equal to 1.2 ⁇ m, for example.
- the buried structure itself is a mesa structure that at least includes the lower cladding layer 12 a , the optical guide layer 11 ca , and the second upper cladding layer 12 ea .
- the micro heater 14 produces heat in response to receiving the supply of electrical current via the electrode pads 15 , and heats the diffraction grating layer 11 cb . If the amount of the supplied electrical current is altered, the diffraction grating layer 11 cb undergoes a change in temperature and a change in refractive index.
- the second optical waveguide portion 20 includes a bifurcating portion 21 , two arm portions 22 and 23 , a ring-shaped waveguide 24 , and a micro heater 25 made of titanium (Ti).
- the bifurcating portion 21 is configured with a 1 ⁇ 2 branching waveguide including a 1 ⁇ 2 multimode interference (MMI) waveguide 21 a ; and has the 2-port side connected to the two arm portions 22 and 23 , and has the 1-port side connected to the first optical waveguide portion 10 . Because of the bifurcating portion 21 , one end of each of the two arm portions 22 and 23 get integrated and are optically coupled with the diffraction grating layer 11 cb.
- MMI multimode interference
- the arm portions 22 and 23 extend in the z-direction and are disposed to sandwich the ring-shaped waveguide 24 .
- the arm portions 22 and 23 are positioned adjacent to the ring-shaped waveguide 24 and are optically coupled with the ring-shaped waveguide 24 by a coupling coefficient ⁇ .
- the coupling coefficient ⁇ has the value equal to 0.2, for example.
- the arm portions 22 and 23 along with the ring-shaped waveguide 24 constitute a ring resonator filter RF 1 .
- the ring resonator filter RF 1 , the bifurcating portion 21 , and a phase adjusting unit 27 constitute a reflective mirror M 1 .
- the micro heater 25 is a ring-shaped heater that is disposed on a SiN protective film formed to cover the ring-shaped waveguide 24 .
- the micro heater 25 produces heat in response to receiving the supply of electrical current, and heats the ring-shaped waveguide 24 . If the amount of the supplied electrical current is altered, the ring-shaped waveguide 24 undergoes a change in temperature and a change in refractive index.
- Each of the bifurcating portion 21 , the arm portions 22 and 23 , and the ring-shaped waveguide 24 has a high-mesa waveguide structure in which an optical guide layer 20 a made of GaInAsP is sandwiched by a lower cladding layer made of the n-type InP and an upper cladding layer made of the p-type InP.
- a micro heater 26 is disposed on some part of the SiN protective film of the arm portion 23 .
- the area below the micro heater 26 functions as the phase adjusting unit 27 for varying the phase of the light.
- the micro heater 26 produces heat in response to receiving the supply of electrical current, and heats the phase adjusting unit 27 . If the amount of the supplied electrical current is altered, the phase adjusting unit 27 undergoes a change in temperature and a change in refractive index.
- the first optical waveguide portion 10 and the second optical waveguide portion 20 constitute an optical resonator C 1 , which is configured with the diffraction grating layer 11 cb and the reflective mirror M 1 that represent a pair of optically-connected wavelength selecting elements.
- the reflective mirror M 1 also includes the phase adjusting unit 27 besides including the bifurcating portion 21 , the arm portion 22 , the arm portion 23 (including the phase adjusting unit 27 ), and the ring-shaped waveguide 24 .
- the phase adjusting unit 27 is disposed inside the reflective mirror M 1 .
- the diffraction grating layer 11 cb generates a first comb-shaped reflectance spectrum having a substantially cyclic reflectance property at substantially predetermined wavelength intervals.
- the ring resonator filter RF 1 generates a second comb-shaped reflectance spectrum having a substantially cyclic reflectance property at substantially predetermined wavelength intervals.
- the second comb-shaped reflectance spectrum has a narrower peak of the full width at half maximum than the peak of the full width at half maximum of the first comb-shaped reflectance spectrum, and has a substantially cyclic reflectance property at different wavelength intervals than the wavelength intervals of the first comb-shaped reflectance spectrum.
- the wavelength dispersion of the refractive index is taken into account, it is necessary to give attention to the fact that the spectral component does not have precisely equal wavelength intervals.
- the inter-peak wavelength interval (free spectral range: FSR) of the first comb-shaped reflectance spectrum is equal to 373 GHz if expressed in frequency of light.
- the inter-peak wavelength interval (FSR) of the second comb-shaped reflectance spectrum is equal to 400 GHz if expressed in frequency of light.
- the configuration is such that one of the peaks of the first comb-shaped reflectance spectrum and one of the peaks of the second comb-shaped reflectance spectrum can be superposed on the wavelength axis.
- Such superposition can be achieved by using at least either the micro heater 14 or the micro heater 25 and by performing at least one of the following: the diffraction grating layer 11 cb is heated using the micro heater 14 so as to vary the refractive index of the diffraction grating layer 11 cb due to the thermo-optic effect, and the first comb-shaped reflectance spectrum is varied by moving it entirely on the wavelength axis; and the ring-shaped waveguide 24 is heated using the micro heater 25 so as to vary the refractive index of the ring-shaped waveguide 24 , and the second comb-shaped reflectance spectrum is varied by moving it entirely on the wavelength axis.
- a resonator mode attributed to the optical resonator C 1 is present.
- the cavity length of the optical resonator C 1 is set in such a way that the interval for the resonator mode (the longitudinal mode interval) becomes equal to or smaller than 25 GHz.
- the wavelength of the resonator mode of the optical resonator C 1 can be fine-tuned by heating the phase adjusting unit 27 using the micro heater 26 , varying the refractive index of the phase adjusting unit 27 , and moving the entire wavelength of the resonator mode on the wavelength axis. That is, the phase adjusting unit 27 represents the portion for actively controlling the optical path length of the optical resonator C 1 .
- the wavelength-tunable laser device 100 is configured in such a way that, when electrical current is injected from the n-side electrode 30 and the p-side electrode 13 to the active core layer 11 a thereby making the active core layer 11 a emit light, laser emission occurs at the wavelength, such as 1550 nm, that either matches with the peak of the spectral component of the first comb-shaped reflectance spectrum, or matches with the peak of the spectral component of the second comb-shaped reflectance spectrum matches, or matches with the resonator mode of the optical resonator C 1 , thereby resulting in the output of a laser light L 1 .
- the wavelength such as 1550 nm
- the laser emission wavelength can be varied by making use of the Vernier effect.
- the refractive index of the diffraction grating layer 11 cb increases due to the thermo-optical effect, and the reflectance spectrum of the diffraction grating layer 11 cb (i.e., the first comb-shaped reflectance spectrum) entirely shifts toward the long-wave side.
- the superimposition occurring in the vicinity of 1550 nm between the peak of the first comb-shaped reflectance spectrum and the peak of the reflectance spectrum of the ring resonator filter RF 1 gets released, and the peak of the first comb-shaped reflectance spectrum gets superposed with some other peak (for example, in the vicinity of 1556 nm) of the second comb-shaped reflectance spectrum.
- the phase adjusting unit 27 is tuned so as to fine-tune the resonator modes, and one of the resonator modes is superposed with the two comb-shaped reflectance spectrums; so that laser emission can be achieved in the vicinity of 1556 nm.
- the diffraction grating layer 11 cb is heated using the micro heater 14 .
- the structure of the third optical waveguide structure portion 10 C is ensured to satisfy a conditional expression given below.
- W mesa represents a mesa width of the mesa structure in the third optical waveguide structure portion 10 C.
- W wg represents a width of the optical guide layer 11 ca , as illustrated in FIG. 3C .
- the optical guide layer 11 ca which is made of a material (GaInAsP) having lower thermal conductivity than the material (InP) of the second upper cladding layer 12 ea , has a greater proportion in the width direction of the mesa structure; it becomes possible to enhance the heating efficiency of the micro heater 14 .
- an optical waveguide structure of a mesa structure which is formed on a substrate made of InP and in which an optical guide layer made of GaInAsP is laid in between an upper cladding portion and a lower cladding portion made of InP, was treated as the calculation model. Then, with respect to that calculation model, the effective refractive index of the optical guide layer was calculated along with calculating the heat resistance at the time when heat was applied from the top surface of the cladding layer. In this calculation model, the width of the optical guide layer is kept constant, and the mesa width of the mesa structure is set to a different value for each calculation model.
- an optical waveguide structure in which the mesa width is equal to the width of the optical guide layer represents an optical waveguide structure of the high-mesa structure; and an optical waveguide structure in which the mesa width is greater than the width of the optical guide layer represents an optical waveguide structure of the buried structure.
- the layers formed on both lateral faces of the optical guide layer are called buried layers.
- the optical guide layer has the thickness of 0.3 ⁇ m and has the width (W wg ) of 2 ⁇ m. Moreover, the optical guide layer has such a composition that the bandgap wavelength becomes equal to 1.2 ⁇ m; has the refractive index of 3.3542 at the wavelength of 1.55 ⁇ m; and is made of GaInAsP having the thermal conductivity of 5 W/Km.
- the upper cladding layer, the lower cladding layer, and the buried layers all have the refractive index of 3.165 at the wavelength of 1.55 ⁇ m; and are made of InP having the thermal conductivity of 68 W/Km.
- the upper cladding layer has the thickness of 1.5 ⁇ m, and the lower cladding layer has the thickness of 1.0 ⁇ m.
- an optical waveguide structure that is configured by replacing the optical guide layer in the optical waveguide structure of the calculation model in the calculation example 1 by a layer made of InP same as the cladding layer was treated as the calculation model, and the heat resistance was calculated when heat was applied from the top surface of the cladding layer.
- FIG. 4 is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the effective refractive index in the calculation example 1.
- the normalized heat resistance represents the amount indicating the rise in temperature in kelvin degrees of the top surface of the upper cladding layer when the heat quantity of 1 W is applied from the top surface of the upper cladding layer.
- the effective refractive index is the value at the wavelength of 1.55 ⁇ m.
- the normalized heat resistance increases at a slow rate.
- the normalized heat resistance increases in an exponential manner. That is, within the range in which “W wg ⁇ W mesa ⁇ 3 ⁇ W wg ” is satisfied, the heat resistance becomes noticeably high, thereby enabling achieving enhancement in the heating efficiency of a heater.
- the heat resistance becomes more noticeably high, thereby enabling achieving further enhancement in the heating efficiency of a heater.
- the normalized heat resistance exponentially increases when the mesa width becomes equal to or smaller than 6 ⁇ m.
- the increase in the normalized heat resistance is more noticeable.
- the increase in the heat resistance is the effect of an increase in the heat gradient occurring due to the narrowing of the width (mesa width) of the flow channel thorough which the applied heat flows; and it is believed that the mesa width is inversely proportional to the heat resistance.
- the heat resistance increases by a large margin that is greater than the prediction based on the result of the calculation example 2.
- the optical guide layer has the composition in which the bandgap wavelength is equal to 1.2 ⁇ m, and is made of GaInAsP having the thermal conductivity of 5 W/Km.
- the thermal conductivity is substantially lower than InP having the thermal conductivity of 68 W/Km.
- the thermal conductivity is substantially lower than InP.
- FIG. 5 is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the normalized heat resistance in the working examples 1 to 3.
- the normalized heat resistance in the working examples 1 to 3 (the right vertical axis) as illustrated in FIG. 5 represents the values normalized at the normalized heat resistance [K/W] in the working example 3 in which the mesa width is equal to 8 ⁇ m; and is non-dimensional in nature.
- the mesa-width dependency of the normalized heat resistance in the working examples 1 to 3 indicates the same tendency as the mesa-width dependency of the normalized heat resistance in the calculation example 1; and thus the validness of the calculation models was confirmed.
- FIG. 6A is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the normalized heat resistance in the cases in which the width of the optical guide layer in the calculation model of the calculation example 1 is varied to 1 ⁇ m, (a calculation example 3), 1.5 ⁇ m (a calculation example 4), 2.5 ⁇ m (a calculation example 5), and 3 ⁇ m (a calculation example 6).
- FIG. 6B is a diagram illustrating the effective refractive index in the calculation example 1 and the calculation examples 3 to 6.
- the calculation example 1 and the calculation examples 3 to 6 are examples in which the calculation was performed within the range in which at least 1 ⁇ m ⁇ W wg ⁇ 3 ⁇ m and 2 ⁇ m ⁇ W mesa ⁇ 4 ⁇ m are satisfied.
- Table 1 is illustrated the effective refractive index and the normalized heat resistance extracted from the calculation examples 1, 4 and 5 for the values of the width W wg and the mesa width W mesa within the range in which 1 ⁇ m ⁇ W wg ⁇ 3 ⁇ m and 2 ⁇ m ⁇ W mesa ⁇ 4 ⁇ m are satisfied.
- the heat resistance becomes high and the heating efficiency of the heater can be enhanced.
- the effective refractive index is substantially constant regardless of the value of the width W mesa .
- the mesa width W mesa is equal to or smaller than 4 ⁇ m, the effective refractive index decreases in proportion to the mesa width W mesa . It implies that, as described earlier, the propagation state of the light in the optical guide layer is affected by the narrowness of the mesa width.
- the state of the third optical waveguide structure portion 10 C is such that the propagation state of the light in the optical guide layer is affected by the narrowness of the mesa width.
- the mesa width is equal to or greater than 250 ⁇ m, for example.
- the effective refractive index is substantially constant regardless of the mesa width.
- the mode field radius or the propagation constant of that light is different than the mode field radius or the propagation constant of the light having the same wavelength and propagating through the optical guide layer 11 ca of the third optical waveguide structure portion 10 C.
- the waveguides having different mode field radii or different propagation constants of the light are directly connected to each other, the mode field radii or the propagation constants undergo changes in a discontinuous manner, thereby causing a substantial optical loss or s substantial optical reflection.
- the active core layer 11 a and the optical guide layer 11 ca are connected via the second optical waveguide structure portion 10 B that functions as a mode field conversion structure.
- the second optical waveguide structure portion 10 B has a tapering shape with the mesa width of the buried structure continually becoming narrower from the first optical waveguide structure portion 10 A toward the third optical waveguide structure portion 10 C (see FIG. 2 ).
- the mode field radius or the propagation constant of the light propagating through the optical guide layer 11 b in the second optical waveguide structure portion 10 B also undergoes changes in a continuous manner from the value in the active core layer 11 a to the value in the optical guide layer 11 ca .
- the buried structure of the second optical waveguide structure portion 10 B has such a mesa width that, in the first optical waveguide structure portion 10 A, the mode field radius or the propagation constant in the optical guide layer 11 b is substantially equal to the mode field radius or the propagation constant in the active core layer 11 a , and has such a mesa width that is equal to the mesa width in the third optical waveguide structure portion 10 C; then the optical loss or the optical reflection can be held down in a more effective manner.
- the third optical waveguide structure portion 10 C of the wavelength-tunable laser device 100 it becomes possible to enhance the heating efficiency for heating the diffraction grating layer 11 cb using the micro heater 14 .
- the wavelength-tunable laser device 100 can be manufactured by following the process described below. Firstly, on an n-type InP substrate constituting the base S, the metal organic chemical vapor deposition (MOCVD) technique is implemented to sequentially deposit the lower cladding layer 12 a and the lower cladding layer in the second optical waveguide portion 20 ; the active core layer 11 a ; and the first upper cladding layer 12 b.
- MOCVD metal organic chemical vapor deposition
- the mask of the SiN film is used as it is as a selective growth mask, and the MOCVD technique is implemented to sequentially deposit the optical guide layers 11 b and 11 ca and the optical guide layer 20 a in the second optical waveguide portion 20 ; the spacer layer 12 f ; the p-type InGaAsP layer serving as the diffraction grating layer 11 cb ; and some part of the second upper cladding layer 12 ea.
- the p-type InP layer is regrown on the entire surface.
- a SiN film is newly deposited, and patterning is performed to form a pattern corresponding to the optical waveguide 11 in the first optical waveguide portion 10 and a pattern corresponding to the optical guide layer in the second optical waveguide portion 20 .
- etching is performed with the SiN film serving as the mask; a stripe mesa structure is formed in the first optical waveguide portion 10 and the second optical waveguide portion 20 ; and the lower cladding layer 12 a is exposed. At that time, etching is performed in the shape of a broad area including the areas corresponding to the bifurcating portion 21 , the arm portions 22 and 23 , and the ring-shaped waveguide 24 .
- the SiN film mask used in the previous process is used as the selective growth mask, and a buried structure is formed by sequentially depositing the exposed lower cladding layer 12 a , the p-type InP buried layer 12 c , and the n-type InP current-blocking layer 12 d according to the MOCVD technique. Subsequently, after the mask of the SiN film is removed, the MOCVD technique is implemented to sequentially deposit, on the entire surface, the second upper cladding layer 12 ea and the p-type InP layer representing the remaining part of the upper cladding layer in the second optical waveguide portion 20 ; and the contact layer 12 eb .
- the contact layer 12 eb is removed from the areas other than the area in which the first optical waveguide structure portion 10 A is to be formed.
- a SiN film is deposited on the entire surface; and patterning is performed for the shapes of the first optical waveguide structure portion 10 A, the second optical waveguide structure portion 10 B, and the third optical waveguide structure portion 10 C, as well as patterning is performed for the waveguides corresponding to the bifurcating portion 21 , the arm portions 22 and 23 , and the ring-shaped waveguide 24 .
- etching is performed with the SiN film serving as the mask; and the mesa structure of the first optical waveguide structure portion 10 A, the second optical waveguide structure portion 10 B, and the third optical waveguide structure portion 10 C is formed, the supporting mesa portions 10 D are formed, and the high-mesa waveguide structure in the second optical waveguide portion 20 is formed.
- This etching is performed, for example, over the depth reaching the base S. That is followed by the formation of the SiN protective film 16 , the insulating member 17 , the n-side electrode 30 , the micro heaters 14 and 26 , the electrode pads 15 , and the wiring pattern.
- the substrate is subjected to bar-shaped cleaving in which a plurality of wavelength-tunable laser devices 100 is arranged; a reflection prevention film is coated on the lateral end faces of the third optical waveguide structure portion 10 C and the end faces of the arm portions 22 and 23 ; and device isolation is performed for each wavelength-tunable laser device 100 , thereby resulting in the completion of the manufacturing of the wavelength-tunable laser devices 100 .
- FIG. 7 is a diagram illustrating a first modification example of the optical waveguide structure.
- An optical-waveguide structure 110 C representing the first modification example of the optical waveguide structure according to the embodiment includes a semiconductor mesa portion 112 in which the position of the diffraction grating layer 11 cb and the position of the optical guide layer 11 ca in the semiconductor mesa portion 12 of the third optical waveguide structure portion 10 C are interchanged. That is, in the optical waveguide structure 110 C, the diffraction grating layer 11 cb is positioned on the side of the lower cladding layer 12 a with respect to the optical guide layer 11 ca .
- the mesa width W mesa of the mesa structure and regarding the width W wg of the optical guide layer 11 ca W wg ⁇ W mesa ⁇ 3 ⁇ W wg is satisfied.
- the mesa width W mesa is equal to or smaller than 4 ⁇ m.
- FIG. 8 is a diagram illustrating a second modification example of the optical waveguide structure.
- An optical waveguide structure 210 C representing the second modification example has a structure in which a semiconductor mesa portion 212 is substituted for the semiconductor mesa portion 12 of the third optical waveguide structure portion 10 C.
- the semiconductor mesa portion 212 is configured by removing the diffraction grating layer 11 cb and the spacer layer 12 f from the semiconductor mesa portion 12 .
- a second upper cladding layer 212 ea is formed up to the area present directly above the optical guide layer 11 ca .
- the optical waveguide structure 210 C heats the optical guide layer 11 ca using the micro heater 14 , varies the refractive index of the optical guide layer 11 ca , and fulfils predetermined functions of phase adjustment.
- W wg ⁇ W mesa ⁇ 3 ⁇ W wg is satisfied.
- the reflection wavelength can be varied as a result of heating.
- the optical waveguide structure 210 C is implemented in an optical waveguide in an optical resonator of a Fabry-Perot semiconductor laser device and if the optical guide layer 11 ca has the function of the active core layer, the laser emission wavelength can be varied as a result of heating. In both cases, it becomes possible to enhance the heating efficiency for heating the optical guide layer 11 ca using the micro heater 14 .
- FIG. 9 is a diagram illustrating a third modification example of the optical waveguide structure.
- An optical waveguide structure 310 C representing the third modification example has a structure in which a semiconductor mesa portion 312 is substituted for the semiconductor mesa portion 12 of the third optical waveguide structure portion 10 C.
- the semiconductor mesa portion 312 has a structure in which a lower cladding layer 312 a and a low thermal conductivity layer 312 g are substituted for the lower cladding layer 12 a of the semiconductor mesa portion 12 .
- the lower cladding layer 312 a is made of lower cladding layers 312 aa and 312 ab .
- the low thermal conductivity layer 312 g is sandwiched between the lower cladding layers 312 aa and 312 ab , and is positioned on the side of the base S with respect to the optical guide layer 11 ca .
- the low thermal conductivity layer 312 g is made of an n-type material (such as AlInAsP or oxidized GaAlInAsP) that has lower thermal conductivity than the InP constituting the lower cladding layer 312 a ; and constitutes a low thermal conductivity area.
- the optical waveguide structure 310 C includes the low thermal conductivity layer 312 g , the heat applied from the micro-heater 14 is prevented from diffusing toward the base S.
- the heating efficiency for heating the optical guide layer 11 ca using the micro heater 14 can be further enhanced.
- the configuration is done as follows. Firstly, in the process of forming the semiconductor mesa portion 312 , a GaAlInAsP layer is deposited at the position at which the low thermal conductivity layer 312 g should be formed. Then, after a mesa structure is formed, annealing is performed under a water-vapor atmosphere with respect to the GaAlInAsP layer having exposed lateral faces, and the GaAlInAsP layer is subjected to thermal oxidation from the exposed lateral faces.
- FIG. 10 is a diagram illustrating a fourth modification example of the optical waveguide structure.
- An optical waveguide structure 410 C representing the fourth modification example has a structure in which a semiconductor mesa portion 412 is substituted for the semiconductor mesa portion 12 of the third optical waveguide structure portion 10 C.
- the semiconductor mesa portion 412 has a structure in which a lower cladding layer 412 a , which includes a supporting area 412 aa extending in one side of the lateral direction with respect to the mesa structure, is substituted for the lower cladding layer 12 a of the semiconductor mesa portion 12 ; and in which a supporting layer 412 h is provided in between the supporting area 412 aa of the lower cladding layer 412 a and the base S.
- the supporting layer 412 h is made of n-type AlInAs, for example. With such a configuration, a hollow area 412 i representing a low thermal conductivity area gets formed in between the portion of the mesa structure of the lower cladding layer 412 a and the base.
- the hollow area 412 i is filled with a gaseous matter such as air.
- the optical waveguide structure 410 C includes the hollow area 412 i , the heat applied from the micro heater 14 is prevented from diffusing toward the base S.
- the heating efficiency for heating the optical guide layer 11 ca using the micro heater 14 can be further enhanced.
- an AlInAs layer representing the supporting layer 412 h is deposited, and then the layers upward of the lower cladding layer 412 a are deposited. Then, at the time of forming the mesa structure, firstly, etching is performed in such a way that the supporting area 412 aa remains intact in the lower cladding layer 412 a , and that is followed by etching in such a way that some part of the AlInAs layer is exposed on the lateral face on the opposite side of the supporting area 412 aa .
- the AlInAs layer in the mesa structure is selectively etch-removed, and the supporting layer 412 h and the hollow area 412 i are formed.
- the diffraction grating is assumed to be sampled grating.
- the type of diffraction grating is not limited to that example, and alternatively the diffraction grating can be superstructure grating or superimposed grating.
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Geometry (AREA)
- Semiconductor Lasers (AREA)
- Optical Integrated Circuits (AREA)
- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
Description
- This application is a continuation of International Application No. PCT/JP2018/004124, filed on Feb. 7, 2018 which claims the benefit of priority of the prior Japanese Patent Application No. 2017-020621, filed on Feb. 7, 2017, the entire contents of which are incorporated herein by reference.
- The present disclosure relates to an optical waveguide structure.
- Regarding a semiconductor laser device that includes an optical waveguide structure, a technology for varying the laser emission wavelength is known in which the refractive indexes of an optical guide layer and a diffraction grating layer, which constitute the optical waveguide structure, are varied by heating the optical waveguide structure using a heater (for example, International Patent Publication No. 2016/152274). In order to enhance the heating efficiency of a heater, technologies for providing a low thermal conductivity layer or a low thermal conductivity area between the optical guide layer and the substrate have been disclosed in Japanese Laid-open Patent Publication No. 2015-12176, Japanese Patent No. 5303580, and U.S. Pat. No. 8,236,589.
- As also disclosed in Japanese Laid-open Patent Publication No. 2015-12176, Japanese Patent No. 5303580, and U.S. Pat. No. 8,236,589; there has been a demand for enhancing the heating efficiency of a heater.
- According to an aspect of the present disclosure, an optical waveguide structure is provided which includes a lower cladding layer positioned on a substrate; an optical guide layer positioned on the lower cladding layer; an upper cladding layer positioned on the optical guide layer; and a heater positioned on the upper cladding layer. The lower cladding layer, the optical guide layer, and the upper cladding layer constitute a mesa structure. The optical guide layer has a lower thermal conductivity than the upper cladding layer. In the optical waveguide structure, an equation “Wwg≤Wmesa≤3×Wwg” is satisfied, wherein Wmesa represents a mesa width of the mesa structure, and Wwg represents a width of the optical guide layer. The optical guide layer occupies one-third or more of the mesa width in a width direction of the mesa structure.
- The above and other objects, features, advantages and technical and industrial significance of this disclosure will be better understood by reading the following detailed description of presently preferred embodiments of the disclosure, when considered in connection with the accompanying drawings.
-
FIG. 1 is a schematic diagram illustrating a configuration of a wavelength-tunable laser device that includes an optical waveguide structure according to an embodiment; -
FIG. 2 is an upper view of a first optical waveguide portion illustrated inFIG. 1 ; -
FIG. 3A is a cross-sectional view along A-A line illustrated inFIG. 2 ; -
FIG. 3B is a cross-sectional view along B-B line illustrated inFIG. 2 ; -
FIG. 3C is a cross-sectional view along C-C line illustrated inFIG. 2 ; -
FIG. 4 is a diagram illustrating the normalized heat resistance in calculation examples 1 and 2 and illustrating the effective refractive index in the calculation example 1; -
FIG. 5 is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the normalized heat resistance in working examples 1 to 3; -
FIG. 6A is a diagram illustrating the normalized heat resistance in calculation examples 1 to 6; -
FIG. 6B is a diagram illustrating the effective refractive index in the calculation example 1 and the calculation examples 3 to 6; -
FIG. 7 is a diagram illustrating a first modification example of the optical waveguide structure; -
FIG. 8 is a diagram illustrating a second modification example of the optical waveguide structure; -
FIG. 9 is a diagram illustrating a third modification example of the optical waveguide structure; and -
FIG. 10 is a diagram illustrating a fourth modification example of the optical waveguide structure. - An exemplary embodiment of the present disclosure is described below with reference to the accompanying drawings. However, the present disclosure is not limited by the embodiment described below. In the drawings, identical or corresponding constituent elements are referred to by the same reference numerals. Moreover, each drawing is schematic in nature, and it needs to be kept in mind that the relationships among the dimensions of the elements or the ratio of the elements may be different than the actual situation. Among the drawings too, there may be portions having different relationships among the dimensions or having different ratios. Moreover, in the drawings, the x-coordinate axis, the y-coordinate axis, and the z-coordinate axis are indicated as necessary, and the directions are explained with reference to those axes.
-
FIG. 1 is a schematic diagram illustrating a configuration of a wavelength-tunable laser device that includes an optical waveguide structure according to an embodiment. A wavelength-tunable laser device 100 includes a firstoptical waveguide portion 10 and a secondoptical waveguide portion 20 that are formed on a common base S. Herein, the base S is made of the n-type InP, for example. Moreover, on the underside surface of the base S, an n-side electrode 30 is formed. The n-side electrode 30 is made of AuGeNi, for example; and makes an ohmic contact with the base S. - The first
optical waveguide portion 10 includes asemiconductor mesa portion 12 with anoptical waveguide 11; includes a p-side electrode 13; includes amicro heater 14 made of titanium (Ti); and includes twoelectrode pads 15. The firstoptical waveguide portion 10 has a buried structure, and theoptical waveguide 11 is formed to extend in the z-direction inside thesemiconductor mesa portion 12. Thesemiconductor mesa portion 12 is configured by layering InP semiconductor layers, and functions as a cladding portion with respect to theoptical waveguide 11. -
FIG. 2 is an upper view of the firstoptical waveguide portion 10. InFIG. 2 , the p-side electrode 13, the micro heater, and theelectrode pads 15 are not illustrated. The firstoptical waveguide portion 10 includes a first opticalwaveguide structure portion 10A, a second opticalwaveguide structure portion 10B, a third opticalwaveguide structure portion 10C, and two supportingmesa portions 10D. The first opticalwaveguide structure portion 10A, the second opticalwaveguide structure portion 10B, and the third opticalwaveguide structure portion 10C are connected in that order. Moreover, in between the pair of the second opticalwaveguide structure portion 10B and the third opticalwaveguide structure portion 10C and the two supportingmesa portions 10D, insulatingmembers 17 are disposed. The insulatingmembers 17 are made of polyimide, for example. - In the
semiconductor mesa portion 12 of the first opticalwaveguide structure portion 10A, the p-side electrode 13 is disposed along theoptical waveguide 11. Meanwhile, in thesemiconductor mesa portion 12, an SiN protective film (described later) is formed, and the p-side electrode 13 makes contact with thesemiconductor mesa portion 12 via an opening formed on the SiN protective film. In thesemiconductor mesa portion 12 of the third opticalwaveguide structure portion 10C, themicro heater 14 is disposed on the SiN protective film and along theoptical waveguide 11. In thesemiconductor mesa portion 12 of the supportingmesa portions 10D, theelectrode pads 15 are disposed on the SiN protective film. Theelectrode pads 15 are connected to themicro heater 14 via a wiring pattern (not illustrated) provided on the insulatingmembers 17. Thus, themicro heater 14 receives the supply of electrical current via theelectrode pads 15 and consequently gets heated. -
FIG. 3A is a cross-sectional view along A-A line illustrated inFIG. 2 ,FIG. 3B is a cross-sectional view along B-B line illustrated inFIG. 2 , andFIG. 3C is a cross-sectional view along C-C line illustrated inFIG. 2 . InFIG. 3A is illustrated the cross-section of the first opticalwaveguide structure portion 10A, inFIG. 3B is illustrated the cross-section of the second opticalwaveguide structure portion 10B, and inFIG. 3C is illustrated the cross-section of the third opticalwaveguide structure portion 10C. - Firstly, the explanation is given about the first optical
waveguide structure portion 10A. As illustrated inFIG. 3A , thesemiconductor mesa portion 12 of the first opticalwaveguide structure portion 10A includes alower cladding layer 12 a, which is made of the n-type InP, on an n-type InP substrate constituting the base S. On thelower cladding layer 12 a, anactive core layer 11 a representing theoptical waveguide 11 in the first opticalwaveguide structure portion 10A is layered. Moreover, on theactive core layer 11 a, a firstupper cladding layer 12 b made of the p-type InP is layered. The upper part of thelower cladding layer 12 a along with theactive core layer 11 a and the firstupper cladding layer 12 b are subjected to etching to form a stripe mesa structure set to have the width (such as 2 μm) that is suitable in guiding, in the single mode, light in the band of 1.55 μm. The sides of the stripe mesa structure (i.e., the right-left direction of the paper sheet) has a buried structure including a current-blocking structure made of a p-type InP buriedlayer 12 c and an n-type InP current-blockinglayer 12 d. Moreover, on the firstupper cladding layer 12 b and the buried structure, a p-type semiconductor layer 12 e is layered. The p-type semiconductor layer 12 e is configured with a secondupper cladding layer 12 ea made of the p-type InP, and acontact layer 12 eb that is made of the p-type InGaAs layered on the secondupper cladding layer 12 ea and that constitutes the uppermost layer of thesemiconductor mesa portion 12. The p-type semiconductor layer 12 e is provided at least from directly above the firstupper cladding layer 12 b across the buried structures present on both sides of the stripe mesa structure. The firstupper cladding layer 12 b and the secondupper cladding layer 12 ea function in an integrated manner as the upper cladding layer with respect to theoptical waveguide 11. In thesemiconductor mesa portion 12, a SiNprotective film 16 is formed to cover thesemiconductor mesa portion 12. The p-side electrode 13 is made of AuZn, is formed on thecontact layer 12 eb, and makes an ohmic contact with thecontact layer 12 eb via anopening 16 a formed on the SiNprotective film 16. With such a configuration, current injection becomes possible from the n-side electrode 30 and the p-side electrode 13 to theactive core layer 11 a. Meanwhile, in the first opticalwaveguide structure portion 10A, the buried structure itself is a mesa structure. - The
active core layer 11 a includes a multiple quantum well structure configured with alternate layering of a plurality of well layers and a plurality of barrier layers, and includes an upper optical confinement layer and a lower optical confinement layer that sandwich the multiple quantum well structure in the vertical direction. Theactive core layer 11 a emits light in response to current injection. The well layers and the barrier layers constituting the multiple quantum well structure of theactive core layer 11 a are made of GaInAsP with mutually different compositions. Moreover, in the embodiment, the emission wavelength band from theactive core layer 11 a is in the band of 1.55 μm. The lower optical confinement layer is made of the n-type GaInAsP. The upper optical confinement layer is made of the p-type GaInAsP. The bandgap wavelength of the lower and upper optical confinement layers is set to be shorter than the bandgap wavelength of theactive core layer 11 a. - The following explanation is given about the second optical
waveguide structure portion 10B. As illustrated inFIG. 3B , thesemiconductor mesa portion 12 of the second opticalwaveguide structure portion 10B has the structure formed by substituting anoptical guide layer 11 b made of GaInAsP for theactive core layer 11 a in the structure illustrated inFIG. 3A and by removing thecontact layer 12 eb. Theoptical guide layer 11 b represents theoptical waveguide 11 in the second opticalwaveguide structure portion 10B. The bandgap wavelength of theoptical guide layer 11 b is desirably shorter than the bandgap wavelength of theactive core layer 11 a and is equal to 1.2 μm, for example. - Meanwhile, as illustrated in
FIG. 2 , in the second opticalwaveguide structure portion 10B, the buried structure itself is a mesa structure having a tapering structure in which the mesa width continually goes on becoming narrower from the first opticalwaveguide structure portion 10A toward the third opticalwaveguide structure portion 10C. For example, in the linking portion with the first opticalwaveguide structure portion 10A, the second opticalwaveguide structure portion 10B has a mesa width Wm equal to 10 μm. Moreover, for example, the second opticalwaveguide structure portion 10B has a length L equal to 100 μm, or 120 μm, or 150 μm. - The following explanation is given about the third optical
waveguide structure portion 10C that is the optical waveguide structure according to the embodiment. As illustrated inFIG. 3C , thesemiconductor mesa portion 12 of the third opticalwaveguide structure portion 10C has a structure formed by substituting anoptical guide layer 11 ca, aspacer layer 12 f, and adiffraction grating layer 11 cb for theoptical guide layer 11 b and the firstupper cladding layer 12 b in the structure illustrated inFIG. 3B . Moreover, themicro heater 14 is disposed on the SiNprotective film 16. Theoptical guide layer 11 ca, thespacer layer 12 f, and thediffraction grating layer 11 cb represent theoptical waveguide 11 in the third opticalwaveguide structure portion 10C. - The
optical guide layer 11 ca is made of GaInAsP. The bandgap wavelength of theoptical guide layer 11 ca is desirably shorter than the bandgap wavelength of theactive core layer 11 a and is equal to 1.2 μm, for example. - The
diffraction grating layer 11 cb includes sampled grating that is provided along theoptical guide layer 11 ca and provided near and directly above theoptical guide layer 11 ca across thespacer layer 12 f made of the p-type InP; and is formed as a diffraction grating layer of the distributed Bragg reflector (DBR) type. That is, thediffraction grating layer 11 cb is positioned on the side of the secondupper cladding layer 12 ea with respect to theoptical guide layer 11 ca. Thediffraction grating layer 11 cb has a configuration in which sampled grating is formed in the P-type GaInAsP layer along the z-direction, and the slits in the diffraction grating are buried with InP. In thediffraction grating layer 11 cb, the grating spacing of the diffraction grating is regular and is sampled, and thus produces a substantially cyclic reflex response with respect to the wavelength. The bandgap wavelength of the p-type GaInAsP layer of thediffraction grating layer 11 cb is desirably shorter than the bandgap wavelength of theactive core layer 11 a and is equal to 1.2 μm, for example. - Meanwhile, in the third optical
waveguide structure portion 10C, the buried structure itself is a mesa structure that at least includes thelower cladding layer 12 a, theoptical guide layer 11 ca, and the secondupper cladding layer 12 ea. Moreover, as described above, themicro heater 14 produces heat in response to receiving the supply of electrical current via theelectrode pads 15, and heats thediffraction grating layer 11 cb. If the amount of the supplied electrical current is altered, thediffraction grating layer 11 cb undergoes a change in temperature and a change in refractive index. - Returning to the explanation with reference to
FIG. 1 , the secondoptical waveguide portion 20 includes a bifurcatingportion 21, twoarm portions waveguide 24, and amicro heater 25 made of titanium (Ti). - The bifurcating
portion 21 is configured with a 1×2 branching waveguide including a 1×2 multimode interference (MMI) waveguide 21 a; and has the 2-port side connected to the twoarm portions optical waveguide portion 10. Because of the bifurcatingportion 21, one end of each of the twoarm portions diffraction grating layer 11 cb. - The
arm portions waveguide 24. Thus, thearm portions waveguide 24 and are optically coupled with the ring-shapedwaveguide 24 by a coupling coefficient κ. The coupling coefficient κ has the value equal to 0.2, for example. Thearm portions waveguide 24 constitute a ring resonator filter RF1. Moreover, the ring resonator filter RF1, the bifurcatingportion 21, and a phase adjusting unit 27 (described below) constitute a reflective mirror M1. Themicro heater 25 is a ring-shaped heater that is disposed on a SiN protective film formed to cover the ring-shapedwaveguide 24. Themicro heater 25 produces heat in response to receiving the supply of electrical current, and heats the ring-shapedwaveguide 24. If the amount of the supplied electrical current is altered, the ring-shapedwaveguide 24 undergoes a change in temperature and a change in refractive index. - Each of the bifurcating
portion 21, thearm portions waveguide 24 has a high-mesa waveguide structure in which anoptical guide layer 20 a made of GaInAsP is sandwiched by a lower cladding layer made of the n-type InP and an upper cladding layer made of the p-type InP. - Moreover, on some part of the SiN protective film of the
arm portion 23, amicro heater 26 is disposed. Of thearm portion 23, the area below themicro heater 26 functions as thephase adjusting unit 27 for varying the phase of the light. Themicro heater 26 produces heat in response to receiving the supply of electrical current, and heats thephase adjusting unit 27. If the amount of the supplied electrical current is altered, thephase adjusting unit 27 undergoes a change in temperature and a change in refractive index. - The first
optical waveguide portion 10 and the secondoptical waveguide portion 20 constitute an optical resonator C1, which is configured with thediffraction grating layer 11 cb and the reflective mirror M1 that represent a pair of optically-connected wavelength selecting elements. The reflective mirror M1 also includes thephase adjusting unit 27 besides including the bifurcatingportion 21, thearm portion 22, the arm portion 23 (including the phase adjusting unit 27), and the ring-shapedwaveguide 24. Thus, thephase adjusting unit 27 is disposed inside the reflective mirror M1. - In the wavelength-
tunable laser device 100, thediffraction grating layer 11 cb generates a first comb-shaped reflectance spectrum having a substantially cyclic reflectance property at substantially predetermined wavelength intervals. The ring resonator filter RF1 generates a second comb-shaped reflectance spectrum having a substantially cyclic reflectance property at substantially predetermined wavelength intervals. The second comb-shaped reflectance spectrum has a narrower peak of the full width at half maximum than the peak of the full width at half maximum of the first comb-shaped reflectance spectrum, and has a substantially cyclic reflectance property at different wavelength intervals than the wavelength intervals of the first comb-shaped reflectance spectrum. However, if the wavelength dispersion of the refractive index is taken into account, it is necessary to give attention to the fact that the spectral component does not have precisely equal wavelength intervals. - As an example of the property of each comb-shaped reflectance spectrum, the inter-peak wavelength interval (free spectral range: FSR) of the first comb-shaped reflectance spectrum is equal to 373 GHz if expressed in frequency of light. The inter-peak wavelength interval (FSR) of the second comb-shaped reflectance spectrum is equal to 400 GHz if expressed in frequency of light.
- In the wavelength-
tunable laser device 100, in order to achieve laser emission, the configuration is such that one of the peaks of the first comb-shaped reflectance spectrum and one of the peaks of the second comb-shaped reflectance spectrum can be superposed on the wavelength axis. Such superposition can be achieved by using at least either themicro heater 14 or themicro heater 25 and by performing at least one of the following: thediffraction grating layer 11 cb is heated using themicro heater 14 so as to vary the refractive index of thediffraction grating layer 11 cb due to the thermo-optic effect, and the first comb-shaped reflectance spectrum is varied by moving it entirely on the wavelength axis; and the ring-shapedwaveguide 24 is heated using themicro heater 25 so as to vary the refractive index of the ring-shapedwaveguide 24, and the second comb-shaped reflectance spectrum is varied by moving it entirely on the wavelength axis. - In the wavelength-
tunable laser device 100, a resonator mode attributed to the optical resonator C1 is present. In the wavelength-tunable laser device 100, the cavity length of the optical resonator C1 is set in such a way that the interval for the resonator mode (the longitudinal mode interval) becomes equal to or smaller than 25 GHz. The wavelength of the resonator mode of the optical resonator C1 can be fine-tuned by heating thephase adjusting unit 27 using themicro heater 26, varying the refractive index of thephase adjusting unit 27, and moving the entire wavelength of the resonator mode on the wavelength axis. That is, thephase adjusting unit 27 represents the portion for actively controlling the optical path length of the optical resonator C1. - The wavelength-
tunable laser device 100 is configured in such a way that, when electrical current is injected from the n-side electrode 30 and the p-side electrode 13 to theactive core layer 11 a thereby making theactive core layer 11 a emit light, laser emission occurs at the wavelength, such as 1550 nm, that either matches with the peak of the spectral component of the first comb-shaped reflectance spectrum, or matches with the peak of the spectral component of the second comb-shaped reflectance spectrum matches, or matches with the resonator mode of the optical resonator C1, thereby resulting in the output of a laser light L1. - Moreover, in the wavelength-
tunable laser device 100, the laser emission wavelength can be varied by making use of the Vernier effect. For example, when thediffraction grating layer 11 cb is heated using themicro heater 14, the refractive index of thediffraction grating layer 11 cb increases due to the thermo-optical effect, and the reflectance spectrum of thediffraction grating layer 11 cb (i.e., the first comb-shaped reflectance spectrum) entirely shifts toward the long-wave side. As a result, the superimposition occurring in the vicinity of 1550 nm between the peak of the first comb-shaped reflectance spectrum and the peak of the reflectance spectrum of the ring resonator filter RF1 (i.e., the second comb-shaped reflectance spectrum) gets released, and the peak of the first comb-shaped reflectance spectrum gets superposed with some other peak (for example, in the vicinity of 1556 nm) of the second comb-shaped reflectance spectrum. Besides, thephase adjusting unit 27 is tuned so as to fine-tune the resonator modes, and one of the resonator modes is superposed with the two comb-shaped reflectance spectrums; so that laser emission can be achieved in the vicinity of 1556 nm. - As described earlier, in the wavelength-
tunable laser device 100, in order to achieve laser emission and to vary the laser emission wavelength, thediffraction grating layer 11 cb is heated using themicro heater 14. In order to enhance the heating efficiency of themicro heater 14, the structure of the third opticalwaveguide structure portion 10C is ensured to satisfy a conditional expression given below. - That is, the following equation is satisfied:
-
W wg ≤W mesa≤3×W wg - wherein, Wmesa represents a mesa width of the mesa structure in the third optical
waveguide structure portion 10C, and - Wwg represents a width of the
optical guide layer 11 ca, as illustrated inFIG. 3C . - Consequently, since the
optical guide layer 11 ca, which is made of a material (GaInAsP) having lower thermal conductivity than the material (InP) of the secondupper cladding layer 12 ea, has a greater proportion in the width direction of the mesa structure; it becomes possible to enhance the heating efficiency of themicro heater 14. - Given below is specific explanation with reference to simulation-based calculation examples. As a calculation example 1, an optical waveguide structure of a mesa structure; which is formed on a substrate made of InP and in which an optical guide layer made of GaInAsP is laid in between an upper cladding portion and a lower cladding portion made of InP, was treated as the calculation model. Then, with respect to that calculation model, the effective refractive index of the optical guide layer was calculated along with calculating the heat resistance at the time when heat was applied from the top surface of the cladding layer. In this calculation model, the width of the optical guide layer is kept constant, and the mesa width of the mesa structure is set to a different value for each calculation model. Moreover, in the calculation model, an optical waveguide structure in which the mesa width is equal to the width of the optical guide layer represents an optical waveguide structure of the high-mesa structure; and an optical waveguide structure in which the mesa width is greater than the width of the optical guide layer represents an optical waveguide structure of the buried structure. In a buried structure, the layers formed on both lateral faces of the optical guide layer are called buried layers.
- The specific calculation parameters that were used in the calculation are as follows. Firstly, the optical guide layer has the thickness of 0.3 μm and has the width (Wwg) of 2 μm. Moreover, the optical guide layer has such a composition that the bandgap wavelength becomes equal to 1.2 μm; has the refractive index of 3.3542 at the wavelength of 1.55 μm; and is made of GaInAsP having the thermal conductivity of 5 W/Km. The upper cladding layer, the lower cladding layer, and the buried layers all have the refractive index of 3.165 at the wavelength of 1.55 μm; and are made of InP having the thermal conductivity of 68 W/Km. The upper cladding layer has the thickness of 1.5 μm, and the lower cladding layer has the thickness of 1.0 μm.
- As a calculation example 2, an optical waveguide structure that is configured by replacing the optical guide layer in the optical waveguide structure of the calculation model in the calculation example 1 by a layer made of InP same as the cladding layer was treated as the calculation model, and the heat resistance was calculated when heat was applied from the top surface of the cladding layer.
-
FIG. 4 is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the effective refractive index in the calculation example 1. The normalized heat resistance represents the amount indicating the rise in temperature in kelvin degrees of the top surface of the upper cladding layer when the heat quantity of 1 W is applied from the top surface of the upper cladding layer. Herein, the effective refractive index is the value at the wavelength of 1.55 μm. - As illustrated in
FIG. 4 , in the calculation example 1, if the mesa width is kept on reducing from about 10 μm, then the normalized heat resistance increases at a slow rate. However, when the mesa width becomes equal to or smaller than 6 μm, the normalized heat resistance increases in an exponential manner. That is, within the range in which “Wwg≤Wmesa≤3×Wwg” is satisfied, the heat resistance becomes noticeably high, thereby enabling achieving enhancement in the heating efficiency of a heater. Moreover, within the range in which “Wwg≤Wmesa≤2×Wwg” is satisfied, the heat resistance becomes more noticeably high, thereby enabling achieving further enhancement in the heating efficiency of a heater. Hence, it is a desirable condition. In the calculation example 2 too, the normalized heat resistance exponentially increases when the mesa width becomes equal to or smaller than 6 μm. However, in the calculation example 1 in which the optical guide layer having low thermal conductivity is present, the increase in the normalized heat resistance is more noticeable. - In the calculation example 2, the increase in the heat resistance is the effect of an increase in the heat gradient occurring due to the narrowing of the width (mesa width) of the flow channel thorough which the applied heat flows; and it is believed that the mesa width is inversely proportional to the heat resistance. In contrast, in the calculation example 1, it was confirmed that the heat resistance increases by a large margin that is greater than the prediction based on the result of the calculation example 2.
- Meanwhile, in the calculation example 1, the optical guide layer has the composition in which the bandgap wavelength is equal to 1.2 μm, and is made of GaInAsP having the thermal conductivity of 5 W/Km. Thus, the thermal conductivity is substantially lower than InP having the thermal conductivity of 68 W/Km. However, regarding GaInAsP, if the composition is transparent with respect to the light having the wavelength between 1.3 μm to 1.6 μm, then the thermal conductivity is substantially lower than InP. Thus, even with respect to GaInAsP having the composition that is transparent with respect to the light having the wavelength between 1.3 μm to 1.6 μm and that has a higher refractive index than InP, it is believed that the relationship between the mesa width and the normalized heat resistance is identical to the result illustrated in
FIG. 4 . - Moreover, as illustrated in
FIG. 4 , the mesa width is equal to 6 μm. That is, when Wmesa=3×Wwg is satisfied, the effective refractive index of the optical guide layer is equal to 3.208. However, when the mesa width falls below 4 μm, the effective refractive index falls in an exponential manner. It implies that, when Wmesa≤2×Wwg is satisfied, as compared to the case in which the mesa width is equal to Wmesa=3×Wwg thereby being sufficiently greater than Wmesa, the propagation state of the light in the optical guide layer is affected by the narrowness of the mesa width. - Subsequently, as working examples 1, 2, and 3; an optical waveguide structure was manufactured according to the calculation model of the calculation example 1, and the heat resistance was measured. In the working examples 1, 2, and 3; the mesa width was set to 2 μm, 3 μm, and 8 μm, respectively.
FIG. 5 is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the normalized heat resistance in the working examples 1 to 3. The normalized heat resistance in the working examples 1 to 3 (the right vertical axis) as illustrated inFIG. 5 represents the values normalized at the normalized heat resistance [K/W] in the working example 3 in which the mesa width is equal to 8 μm; and is non-dimensional in nature. As illustrated inFIG. 5 , the mesa-width dependency of the normalized heat resistance in the working examples 1 to 3 indicates the same tendency as the mesa-width dependency of the normalized heat resistance in the calculation example 1; and thus the validness of the calculation models was confirmed. -
FIG. 6A is a diagram illustrating the normalized heat resistance in the calculation examples 1 and 2 and illustrating the normalized heat resistance in the cases in which the width of the optical guide layer in the calculation model of the calculation example 1 is varied to 1 μm, (a calculation example 3), 1.5 μm (a calculation example 4), 2.5 μm (a calculation example 5), and 3 μm (a calculation example 6).FIG. 6B is a diagram illustrating the effective refractive index in the calculation example 1 and the calculation examples 3 to 6. The calculation example 1 and the calculation examples 3 to 6 are examples in which the calculation was performed within the range in which at least 1 μm≤Wwg≤3 μm and 2 μm≤Wmesa≤4 μm are satisfied. In Table 1 is illustrated the effective refractive index and the normalized heat resistance extracted from the calculation examples 1, 4 and 5 for the values of the width Wwg and the mesa width Wmesa within the range in which 1 μm≤Wwg≤3 μm and 2 μm≤Wmesa≤4 μm are satisfied. -
TABLE 1 Effective Standardized Wwg Wmesa refractive heat resistance [μm] [μm] index [K/W] 2.0 4.0 3.208 0.015 2.0 3.0 3.207 0.025 2.0 2.5 3.205 0.035 2.0 2.0 3.198 0.063 2.0 5.0 3.208 0.011 1.5 3.0 3.201 0.021 2.5 4.0 3.212 0.018 - As illustrated in
FIG. 6A , regardless of the value of the width Wwg, as long as Wmesa≤4 is satisfied, the heat resistance becomes high and the heating efficiency of the heater can be enhanced. Moreover, as illustrated inFIG. 6B , when the mesa width Wmesa is greater than 4 μm, the effective refractive index is substantially constant regardless of the value of the width Wmesa. However, when the mesa width Wmesa is equal to or smaller than 4 μm, the effective refractive index decreases in proportion to the mesa width Wmesa. It implies that, as described earlier, the propagation state of the light in the optical guide layer is affected by the narrowness of the mesa width. - Herein, it is assumed that Wwg≤Wmesa≤2×Wwg is satisfied in the third optical
waveguide structure portion 10C. In that case, the state of the third opticalwaveguide structure portion 10C is such that the propagation state of the light in the optical guide layer is affected by the narrowness of the mesa width. On the other hand, in the first opticalwaveguide structure portion 10A, there is sufficiently large mesa width with respect to the width of theactive core layer 11 a representing the optical guide layer, and the mesa width is equal to or greater than 250 μm, for example. Thus, in the first opticalwaveguide structure portion 10A, the effective refractive index is substantially constant regardless of the mesa width. Hence, in the first opticalwaveguide structure portion 10A, regarding the light having a predetermined wavelength (such as 1.55 μm) and propagating through theactive core layer 11 a, the mode field radius or the propagation constant of that light is different than the mode field radius or the propagation constant of the light having the same wavelength and propagating through theoptical guide layer 11 ca of the third opticalwaveguide structure portion 10C. When the waveguides having different mode field radii or different propagation constants of the light are directly connected to each other, the mode field radii or the propagation constants undergo changes in a discontinuous manner, thereby causing a substantial optical loss or s substantial optical reflection. - In that regard, in the wavelength-
tunable laser device 100, theactive core layer 11 a and theoptical guide layer 11 ca are connected via the second opticalwaveguide structure portion 10B that functions as a mode field conversion structure. As described earlier, the second opticalwaveguide structure portion 10B has a tapering shape with the mesa width of the buried structure continually becoming narrower from the first opticalwaveguide structure portion 10A toward the third opticalwaveguide structure portion 10C (seeFIG. 2 ). As a result, the mode field radius or the propagation constant of the light propagating through theoptical guide layer 11 b in the second opticalwaveguide structure portion 10B also undergoes changes in a continuous manner from the value in theactive core layer 11 a to the value in theoptical guide layer 11 ca. That enables holding down the optical loss or the optical reflection. More desirably, if the buried structure of the second opticalwaveguide structure portion 10B has such a mesa width that, in the first opticalwaveguide structure portion 10A, the mode field radius or the propagation constant in theoptical guide layer 11 b is substantially equal to the mode field radius or the propagation constant in theactive core layer 11 a, and has such a mesa width that is equal to the mesa width in the third opticalwaveguide structure portion 10C; then the optical loss or the optical reflection can be held down in a more effective manner. - As explained above, in the third optical
waveguide structure portion 10C of the wavelength-tunable laser device 100, it becomes possible to enhance the heating efficiency for heating thediffraction grating layer 11 cb using themicro heater 14. - Meanwhile, the wavelength-
tunable laser device 100 can be manufactured by following the process described below. Firstly, on an n-type InP substrate constituting the base S, the metal organic chemical vapor deposition (MOCVD) technique is implemented to sequentially deposit thelower cladding layer 12 a and the lower cladding layer in the secondoptical waveguide portion 20; theactive core layer 11 a; and the firstupper cladding layer 12 b. - Subsequently, after depositing a SiN film on the entire surface, patterning is performed on the SiN film. Then, etching is performed with the SiN film serving as the mask and, other than the area in which the first optical
waveguide structure portion 10A is to be formed, theactive core layer 11 a and the firstupper cladding layer 12 b are removed from the entire remaining area. Moreover, the mask of the SiN film is used as it is as a selective growth mask, and the MOCVD technique is implemented to sequentially deposit the optical guide layers 11 b and 11 ca and theoptical guide layer 20 a in the secondoptical waveguide portion 20; thespacer layer 12 f; the p-type InGaAsP layer serving as thediffraction grating layer 11 cb; and some part of the secondupper cladding layer 12 ea. - Subsequently, after the mask of the SiN film is removed and after a SiN film is deposited on the entire surface, patterning of diffraction grating is performed on the SiN film of the area in which the
diffraction grating layer 11 cb is to be formed. Then, etching is performed with the SiN film serving as the mask; grating grooves are formed that would serve as the diffraction grating in the p-type InGaAsP layer; and the p-type InGaAsP layer is removed from all positions other than the position of forming thediffraction grating layer 11 cb. - Subsequently, after the mask of the SiN film is removed, the p-type InP layer is regrown on the entire surface. Then, a SiN film is newly deposited, and patterning is performed to form a pattern corresponding to the
optical waveguide 11 in the firstoptical waveguide portion 10 and a pattern corresponding to the optical guide layer in the secondoptical waveguide portion 20. Subsequently, etching is performed with the SiN film serving as the mask; a stripe mesa structure is formed in the firstoptical waveguide portion 10 and the secondoptical waveguide portion 20; and thelower cladding layer 12 a is exposed. At that time, etching is performed in the shape of a broad area including the areas corresponding to the bifurcatingportion 21, thearm portions waveguide 24. - Then, the SiN film mask used in the previous process is used as the selective growth mask, and a buried structure is formed by sequentially depositing the exposed
lower cladding layer 12 a, the p-type InP buriedlayer 12 c, and the n-type InP current-blockinglayer 12 d according to the MOCVD technique. Subsequently, after the mask of the SiN film is removed, the MOCVD technique is implemented to sequentially deposit, on the entire surface, the secondupper cladding layer 12 ea and the p-type InP layer representing the remaining part of the upper cladding layer in the secondoptical waveguide portion 20; and thecontact layer 12 eb. Then, thecontact layer 12 eb is removed from the areas other than the area in which the first opticalwaveguide structure portion 10A is to be formed. Subsequently, a SiN film is deposited on the entire surface; and patterning is performed for the shapes of the first opticalwaveguide structure portion 10A, the second opticalwaveguide structure portion 10B, and the third opticalwaveguide structure portion 10C, as well as patterning is performed for the waveguides corresponding to the bifurcatingportion 21, thearm portions waveguide 24. Then, etching is performed with the SiN film serving as the mask; and the mesa structure of the first opticalwaveguide structure portion 10A, the second opticalwaveguide structure portion 10B, and the third opticalwaveguide structure portion 10C is formed, the supportingmesa portions 10D are formed, and the high-mesa waveguide structure in the secondoptical waveguide portion 20 is formed. This etching is performed, for example, over the depth reaching the base S. That is followed by the formation of the SiNprotective film 16, the insulatingmember 17, the n-side electrode 30, themicro heaters electrode pads 15, and the wiring pattern. Lastly, the substrate is subjected to bar-shaped cleaving in which a plurality of wavelength-tunable laser devices 100 is arranged; a reflection prevention film is coated on the lateral end faces of the third opticalwaveguide structure portion 10C and the end faces of thearm portions tunable laser device 100, thereby resulting in the completion of the manufacturing of the wavelength-tunable laser devices 100. - The optical waveguide structure according to the present disclosure is not limited to the embodiment described above, and can be modified into various other forms.
FIG. 7 is a diagram illustrating a first modification example of the optical waveguide structure. An optical-waveguide structure 110C representing the first modification example of the optical waveguide structure according to the embodiment includes asemiconductor mesa portion 112 in which the position of thediffraction grating layer 11 cb and the position of theoptical guide layer 11 ca in thesemiconductor mesa portion 12 of the third opticalwaveguide structure portion 10C are interchanged. That is, in theoptical waveguide structure 110C, thediffraction grating layer 11 cb is positioned on the side of thelower cladding layer 12 a with respect to theoptical guide layer 11 ca. In theoptical waveguide structure 110C too, regarding the mesa width Wmesa of the mesa structure and regarding the width Wwg of theoptical guide layer 11 ca, Wwg≤Wmesa≤3×Wwg is satisfied. Moreover, the mesa width Wmesa is equal to or smaller than 4 μm. As a result, even if the structure is such that thediffraction grating layer 11 cb is positioned on the opposite side of themicro heater 14 with respect to theoptical guide layer 11 ca, it becomes possible to enhance the heating efficiency for heating thediffraction grating layer 11 cb using themicro heater 14. -
FIG. 8 is a diagram illustrating a second modification example of the optical waveguide structure. Anoptical waveguide structure 210C representing the second modification example has a structure in which asemiconductor mesa portion 212 is substituted for thesemiconductor mesa portion 12 of the third opticalwaveguide structure portion 10C. Thesemiconductor mesa portion 212 is configured by removing thediffraction grating layer 11 cb and thespacer layer 12 f from thesemiconductor mesa portion 12. In thesemiconductor mesa portion 212, a secondupper cladding layer 212 ea is formed up to the area present directly above theoptical guide layer 11 ca. Theoptical waveguide structure 210C heats theoptical guide layer 11 ca using themicro heater 14, varies the refractive index of theoptical guide layer 11 ca, and fulfils predetermined functions of phase adjustment. In theoptical waveguide structure 210C too, regarding the mesa width Wmesa of the mesa structure and regarding the width Wwg of theoptical guide layer 11 ca, Wwg≤Wmesa≤3×Wwg is satisfied. As a result, it becomes possible to enhance the heating efficiency for heating theoptical guide layer 11 ca using themicro heater 14. Meanwhile, if theoptical guide layer 11 ca has the function of diffraction grating, then the reflection wavelength can be varied as a result of heating. Moreover, if theoptical waveguide structure 210C is implemented in an optical waveguide in an optical resonator of a Fabry-Perot semiconductor laser device and if theoptical guide layer 11 ca has the function of the active core layer, the laser emission wavelength can be varied as a result of heating. In both cases, it becomes possible to enhance the heating efficiency for heating theoptical guide layer 11 ca using themicro heater 14. -
FIG. 9 is a diagram illustrating a third modification example of the optical waveguide structure. Anoptical waveguide structure 310C representing the third modification example has a structure in which asemiconductor mesa portion 312 is substituted for thesemiconductor mesa portion 12 of the third opticalwaveguide structure portion 10C. Thesemiconductor mesa portion 312 has a structure in which alower cladding layer 312 a and a lowthermal conductivity layer 312 g are substituted for thelower cladding layer 12 a of thesemiconductor mesa portion 12. Thelower cladding layer 312 a is made of lower cladding layers 312 aa and 312 ab. The lowthermal conductivity layer 312 g is sandwiched between the lower cladding layers 312 aa and 312 ab, and is positioned on the side of the base S with respect to theoptical guide layer 11 ca. The lowthermal conductivity layer 312 g is made of an n-type material (such as AlInAsP or oxidized GaAlInAsP) that has lower thermal conductivity than the InP constituting thelower cladding layer 312 a; and constitutes a low thermal conductivity area. - Since the
optical waveguide structure 310C includes the lowthermal conductivity layer 312 g, the heat applied from the micro-heater 14 is prevented from diffusing toward the base S. Thus, in combination with the effect attributed to the fact that Wwg≤Wmesa≤3×Wwg is satisfied, the heating efficiency for heating theoptical guide layer 11 ca using themicro heater 14 can be further enhanced. - Meanwhile, when the low
thermal conductivity layer 312 g is configured using oxidized GaAlInAsP, the configuration is done as follows. Firstly, in the process of forming thesemiconductor mesa portion 312, a GaAlInAsP layer is deposited at the position at which the lowthermal conductivity layer 312 g should be formed. Then, after a mesa structure is formed, annealing is performed under a water-vapor atmosphere with respect to the GaAlInAsP layer having exposed lateral faces, and the GaAlInAsP layer is subjected to thermal oxidation from the exposed lateral faces. -
FIG. 10 is a diagram illustrating a fourth modification example of the optical waveguide structure. Anoptical waveguide structure 410C representing the fourth modification example has a structure in which asemiconductor mesa portion 412 is substituted for thesemiconductor mesa portion 12 of the third opticalwaveguide structure portion 10C. Thesemiconductor mesa portion 412 has a structure in which alower cladding layer 412 a, which includes a supportingarea 412 aa extending in one side of the lateral direction with respect to the mesa structure, is substituted for thelower cladding layer 12 a of thesemiconductor mesa portion 12; and in which a supportinglayer 412 h is provided in between the supportingarea 412 aa of thelower cladding layer 412 a and the base S. The supportinglayer 412 h is made of n-type AlInAs, for example. With such a configuration, ahollow area 412 i representing a low thermal conductivity area gets formed in between the portion of the mesa structure of thelower cladding layer 412 a and the base. Thehollow area 412 i is filled with a gaseous matter such as air. - Since the
optical waveguide structure 410C includes thehollow area 412 i, the heat applied from themicro heater 14 is prevented from diffusing toward the base S. Thus, in combination with the effect attributed to the fact that Wwg≤Wmesa≤3×Wwg is satisfied, the heating efficiency for heating theoptical guide layer 11 ca using themicro heater 14 can be further enhanced. - Given below is the explanation of a manufacturing method for manufacturing the
optical waveguide structure 410C. Firstly, on an n-type InP substrate, an AlInAs layer representing the supportinglayer 412 h is deposited, and then the layers upward of thelower cladding layer 412 a are deposited. Then, at the time of forming the mesa structure, firstly, etching is performed in such a way that the supportingarea 412 aa remains intact in thelower cladding layer 412 a, and that is followed by etching in such a way that some part of the AlInAs layer is exposed on the lateral face on the opposite side of the supportingarea 412 aa. Subsequently, for example, using an etching solution of the hydrofluoric acid type, the AlInAs layer in the mesa structure is selectively etch-removed, and the supportinglayer 412 h and thehollow area 412 i are formed. - Meanwhile, in the embodiment and the modification examples described above, the diffraction grating is assumed to be sampled grating. However, the type of diffraction grating is not limited to that example, and alternatively the diffraction grating can be superstructure grating or superimposed grating.
- According to the present disclosure, it becomes possible to implement an optical waveguide structure in which the heating efficiency of a heater is enhanced.
- Although the disclosure has been described with respect to specific embodiments for a complete and clear disclosure, the appended claims are not to be thus limited but are to be construed as embodying all modifications and alternative constructions that may occur to one skilled in the art that fairly fall within the basic teaching herein set forth.
Claims (13)
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JPJP2017-020621 | 2017-02-07 | ||
JP2017020621 | 2017-02-07 | ||
JP2017-020621 | 2017-09-21 | ||
PCT/JP2018/004124 WO2018147307A1 (en) | 2017-02-07 | 2018-02-07 | Optical waveguide structure |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2018/004124 Continuation WO2018147307A1 (en) | 2017-02-07 | 2018-02-07 | Optical waveguide structure |
Publications (2)
Publication Number | Publication Date |
---|---|
US20190363516A1 true US20190363516A1 (en) | 2019-11-28 |
US11482838B2 US11482838B2 (en) | 2022-10-25 |
Family
ID=63107544
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US16/532,696 Active 2038-02-24 US11482838B2 (en) | 2017-02-07 | 2019-08-06 | Optical waveguide structure |
Country Status (4)
Country | Link |
---|---|
US (1) | US11482838B2 (en) |
JP (1) | JP7145765B2 (en) |
CN (1) | CN110249245B (en) |
WO (1) | WO2018147307A1 (en) |
Families Citing this family (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN111142187B (en) * | 2020-01-16 | 2024-06-11 | 中国人民解放军国防科技大学 | Filter based on double-guided-mode resonance grating mode coupling mechanism |
JPWO2021149647A1 (en) * | 2020-01-22 | 2021-07-29 | ||
JP7444622B2 (en) * | 2020-01-29 | 2024-03-06 | 古河電気工業株式会社 | Optical semiconductor devices and integrated semiconductor lasers |
CN114552383B (en) * | 2020-11-27 | 2023-07-18 | 山东华光光电子股份有限公司 | Red light semiconductor laser without aluminum active region and preparation method thereof |
Citations (28)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4759023A (en) * | 1985-01-09 | 1988-07-19 | Nec Corporation | Monolithically integrated semiconductor optical device and method of fabricating same |
US5082799A (en) * | 1990-09-14 | 1992-01-21 | Gte Laboratories Incorporated | Method for fabricating indium phosphide/indium gallium arsenide phosphide buried heterostructure semiconductor lasers |
US5222091A (en) * | 1990-09-14 | 1993-06-22 | Gte Laboratories Incorporated | Structure for indium phosphide/indium gallium arsenide phosphide buried heterostructure semiconductor |
JPH0653606A (en) * | 1992-07-27 | 1994-02-25 | Nippon Telegr & Teleph Corp <Ntt> | Semiconductor laser |
JPH07106691A (en) * | 1993-10-05 | 1995-04-21 | Nippon Telegr & Teleph Corp <Ntt> | Integrated light source with external modulator and driving method therefor |
JPH08279648A (en) * | 1995-04-05 | 1996-10-22 | Furukawa Electric Co Ltd:The | Manufacture of distributed feedback semiconductor laser device |
US6226310B1 (en) * | 1997-09-29 | 2001-05-01 | Mitsubishi Denki Kabushiki Kaisha | Semiconductor optical device |
US6396854B1 (en) * | 1997-12-15 | 2002-05-28 | Mitsubishi Denki Kabushiki Kaisha | Encased semiconductor laser device in contact with a fluid and method of producing the laser device |
US20020141682A1 (en) * | 2001-04-02 | 2002-10-03 | Sang-Wan Ryu | Spot-size converter integratrd laser diode and method for fabricating the same |
US6977953B2 (en) * | 2001-07-27 | 2005-12-20 | Sanyo Electric Co., Ltd. | Nitride-based semiconductor light-emitting device and method of fabricating the same |
US20080137180A1 (en) * | 2006-12-07 | 2008-06-12 | Electronics And Telecommunications Research Institute | Reflective semiconductor optical amplifier (r-soa) and superluminescent diode (sld) |
US20100303115A1 (en) * | 2009-05-27 | 2010-12-02 | Sumitomo Electric Industries, Ltd. | Method for manufacturing semiconductor laser diode |
US7859745B2 (en) * | 2007-06-15 | 2010-12-28 | Fujitsu Limited | Semiconductor optical amplifying device, semiconductor optical amplifying system and semiconductor optical integrated element |
US20110085572A1 (en) * | 2009-10-13 | 2011-04-14 | Skorpios Technologies, Inc. | Method and system for hybrid integration of a tunable laser |
US20110305255A1 (en) * | 2010-06-10 | 2011-12-15 | Mitsubishi Electric Corporation | Semiconductor optical integrated element and method for manufacturing the same |
US20120128375A1 (en) * | 2009-07-30 | 2012-05-24 | Furukawa Electric Co., Ltd. | Integrated semiconductor laser element, semiconductor laser module, and optical transmission system |
US20120321244A1 (en) * | 2011-06-15 | 2012-12-20 | Opnext Japan, Inc | Optical semiconductor device, and manufacturing method thereof |
US20130003762A1 (en) * | 2011-06-29 | 2013-01-03 | Sumitomo Electric Industries, Ltd. | Wavelength tunable laser diode |
US20130122623A1 (en) * | 2011-11-16 | 2013-05-16 | Mitsubishi Electric Corporation | Method of manufacturing optical semiconductor device |
US20130136391A1 (en) * | 2011-11-28 | 2013-05-30 | Mitsubishi Electric Corporation | Optical semiconductor device |
US8488637B2 (en) * | 2010-03-25 | 2013-07-16 | Sumitomo Electric Industries Ltd. | Semiconductor laser |
JP2013165123A (en) * | 2012-02-09 | 2013-08-22 | Furukawa Electric Co Ltd:The | Method of manufacturing semiconductor element having semiconductor forward mesa structure, and method of manufacturing integrated semiconductor light emitting element containing semiconductor element |
US20130235890A1 (en) * | 2011-09-07 | 2013-09-12 | Skorpios Technologies, Inc. | Tunable hybrid laser with carrier-induced phase control |
US20130272326A1 (en) * | 2012-04-16 | 2013-10-17 | Mitsubishi Electric Corporation | Modulator integrated laser device |
US20150132002A1 (en) * | 2013-11-13 | 2015-05-14 | Agency For Science, Technology And Research | Integrated laser and method of fabrication thereof |
US20160218484A1 (en) * | 2015-01-27 | 2016-07-28 | Huawei Technologies Co., Ltd. | Tunable laser and method of tuning a laser |
US20160268768A1 (en) * | 2015-03-11 | 2016-09-15 | Mitsubishi Electric Corporation | Method for manufacturing optical semiconductor device |
US20200379174A1 (en) * | 2019-05-28 | 2020-12-03 | Ciena Corporation | Monolithically Integrated Gain Element |
Family Cites Families (16)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP3064118B2 (en) * | 1992-09-16 | 2000-07-12 | アンリツ株式会社 | Distributed reflection semiconductor laser |
JPH1154841A (en) * | 1997-07-30 | 1999-02-26 | Furukawa Electric Co Ltd:The | Semiconductor laser device and its manufacture |
GB2409570B (en) * | 2003-10-10 | 2007-02-14 | Agilent Technologies Inc | Optoelectronic device having a discrete bragg reflector and an electro-absorption modulator |
JP4685535B2 (en) * | 2005-07-21 | 2011-05-18 | 日本電信電話株式会社 | Thermo-optic phase modulator and manufacturing method thereof |
JP2007273644A (en) * | 2006-03-30 | 2007-10-18 | Eudyna Devices Inc | Optical semiconductor device, laser chip, and laser module |
US7760777B2 (en) | 2007-04-13 | 2010-07-20 | Finisar Corporation | DBR laser with improved thermal tuning efficiency |
JP5303580B2 (en) | 2011-01-11 | 2013-10-02 | 住友電工デバイス・イノベーション株式会社 | Optical semiconductor device, laser chip and laser module |
JP2012174938A (en) * | 2011-02-22 | 2012-09-10 | Sumitomo Electric Ind Ltd | Optical semiconductor device and method of manufacturing the same |
JPWO2013115179A1 (en) * | 2012-01-30 | 2015-05-11 | 古河電気工業株式会社 | Semiconductor optical device, integrated semiconductor optical device, and semiconductor optical device module |
JP6067231B2 (en) * | 2012-02-21 | 2017-01-25 | 古河電気工業株式会社 | Optical filter and semiconductor laser device |
JP2014149323A (en) * | 2013-01-30 | 2014-08-21 | Furukawa Electric Co Ltd:The | Semiconductor optical modulator |
WO2014126261A1 (en) | 2013-02-18 | 2014-08-21 | 古河電気工業株式会社 | Semiconductor laser element, integrated semiconductor laser element, and method for manufacturing semiconductor laser element |
JP6212754B2 (en) | 2013-06-28 | 2017-10-18 | 住友電工デバイス・イノベーション株式会社 | Optical semiconductor device and manufacturing method thereof |
JP6416553B2 (en) * | 2014-09-02 | 2018-10-31 | 住友電気工業株式会社 | Semiconductor device and method for manufacturing semiconductor device |
WO2016152274A1 (en) | 2015-03-20 | 2016-09-29 | 古河電気工業株式会社 | Variable wavelength laser element and laser module |
JP6684094B2 (en) | 2015-03-20 | 2020-04-22 | 古河電気工業株式会社 | Tunable laser device and laser module |
-
2018
- 2018-02-07 JP JP2018567454A patent/JP7145765B2/en active Active
- 2018-02-07 WO PCT/JP2018/004124 patent/WO2018147307A1/en active Application Filing
- 2018-02-07 CN CN201880009829.4A patent/CN110249245B/en active Active
-
2019
- 2019-08-06 US US16/532,696 patent/US11482838B2/en active Active
Patent Citations (28)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4759023A (en) * | 1985-01-09 | 1988-07-19 | Nec Corporation | Monolithically integrated semiconductor optical device and method of fabricating same |
US5082799A (en) * | 1990-09-14 | 1992-01-21 | Gte Laboratories Incorporated | Method for fabricating indium phosphide/indium gallium arsenide phosphide buried heterostructure semiconductor lasers |
US5222091A (en) * | 1990-09-14 | 1993-06-22 | Gte Laboratories Incorporated | Structure for indium phosphide/indium gallium arsenide phosphide buried heterostructure semiconductor |
JPH0653606A (en) * | 1992-07-27 | 1994-02-25 | Nippon Telegr & Teleph Corp <Ntt> | Semiconductor laser |
JPH07106691A (en) * | 1993-10-05 | 1995-04-21 | Nippon Telegr & Teleph Corp <Ntt> | Integrated light source with external modulator and driving method therefor |
JPH08279648A (en) * | 1995-04-05 | 1996-10-22 | Furukawa Electric Co Ltd:The | Manufacture of distributed feedback semiconductor laser device |
US6226310B1 (en) * | 1997-09-29 | 2001-05-01 | Mitsubishi Denki Kabushiki Kaisha | Semiconductor optical device |
US6396854B1 (en) * | 1997-12-15 | 2002-05-28 | Mitsubishi Denki Kabushiki Kaisha | Encased semiconductor laser device in contact with a fluid and method of producing the laser device |
US20020141682A1 (en) * | 2001-04-02 | 2002-10-03 | Sang-Wan Ryu | Spot-size converter integratrd laser diode and method for fabricating the same |
US6977953B2 (en) * | 2001-07-27 | 2005-12-20 | Sanyo Electric Co., Ltd. | Nitride-based semiconductor light-emitting device and method of fabricating the same |
US20080137180A1 (en) * | 2006-12-07 | 2008-06-12 | Electronics And Telecommunications Research Institute | Reflective semiconductor optical amplifier (r-soa) and superluminescent diode (sld) |
US7859745B2 (en) * | 2007-06-15 | 2010-12-28 | Fujitsu Limited | Semiconductor optical amplifying device, semiconductor optical amplifying system and semiconductor optical integrated element |
US20100303115A1 (en) * | 2009-05-27 | 2010-12-02 | Sumitomo Electric Industries, Ltd. | Method for manufacturing semiconductor laser diode |
US20120128375A1 (en) * | 2009-07-30 | 2012-05-24 | Furukawa Electric Co., Ltd. | Integrated semiconductor laser element, semiconductor laser module, and optical transmission system |
US20110085572A1 (en) * | 2009-10-13 | 2011-04-14 | Skorpios Technologies, Inc. | Method and system for hybrid integration of a tunable laser |
US8488637B2 (en) * | 2010-03-25 | 2013-07-16 | Sumitomo Electric Industries Ltd. | Semiconductor laser |
US20110305255A1 (en) * | 2010-06-10 | 2011-12-15 | Mitsubishi Electric Corporation | Semiconductor optical integrated element and method for manufacturing the same |
US20120321244A1 (en) * | 2011-06-15 | 2012-12-20 | Opnext Japan, Inc | Optical semiconductor device, and manufacturing method thereof |
US20130003762A1 (en) * | 2011-06-29 | 2013-01-03 | Sumitomo Electric Industries, Ltd. | Wavelength tunable laser diode |
US20130235890A1 (en) * | 2011-09-07 | 2013-09-12 | Skorpios Technologies, Inc. | Tunable hybrid laser with carrier-induced phase control |
US20130122623A1 (en) * | 2011-11-16 | 2013-05-16 | Mitsubishi Electric Corporation | Method of manufacturing optical semiconductor device |
US20130136391A1 (en) * | 2011-11-28 | 2013-05-30 | Mitsubishi Electric Corporation | Optical semiconductor device |
JP2013165123A (en) * | 2012-02-09 | 2013-08-22 | Furukawa Electric Co Ltd:The | Method of manufacturing semiconductor element having semiconductor forward mesa structure, and method of manufacturing integrated semiconductor light emitting element containing semiconductor element |
US20130272326A1 (en) * | 2012-04-16 | 2013-10-17 | Mitsubishi Electric Corporation | Modulator integrated laser device |
US20150132002A1 (en) * | 2013-11-13 | 2015-05-14 | Agency For Science, Technology And Research | Integrated laser and method of fabrication thereof |
US20160218484A1 (en) * | 2015-01-27 | 2016-07-28 | Huawei Technologies Co., Ltd. | Tunable laser and method of tuning a laser |
US20160268768A1 (en) * | 2015-03-11 | 2016-09-15 | Mitsubishi Electric Corporation | Method for manufacturing optical semiconductor device |
US20200379174A1 (en) * | 2019-05-28 | 2020-12-03 | Ciena Corporation | Monolithically Integrated Gain Element |
Also Published As
Publication number | Publication date |
---|---|
CN110249245A (en) | 2019-09-17 |
US11482838B2 (en) | 2022-10-25 |
WO2018147307A1 (en) | 2018-08-16 |
JP7145765B2 (en) | 2022-10-03 |
CN110249245B (en) | 2021-02-19 |
JPWO2018147307A1 (en) | 2019-11-21 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US11482838B2 (en) | Optical waveguide structure | |
JP2011204895A (en) | Semiconductor laser | |
KR102642580B1 (en) | Tunable distributed feedback laser diode with thin film heater | |
JP6667325B2 (en) | Semiconductor optical device | |
JP3689483B2 (en) | Multiple wavelength laser | |
JP6782083B2 (en) | Semiconductor optical devices and their manufacturing methods | |
JP3681693B2 (en) | Semiconductor laser and semiconductor optical integrated circuit including this element | |
JPH0750815B2 (en) | Method for manufacturing semiconductor optical integrated device | |
JP5272859B2 (en) | Semiconductor laser element | |
JP7353766B2 (en) | Ring resonator filter and wavelength tunable laser element | |
JPH0697604A (en) | Distributed reflection type semiconductor laser | |
JP2002057405A (en) | Semiconductor laser device and its manufacturing method | |
JP5163355B2 (en) | Semiconductor laser device | |
JPH08274406A (en) | Distributed feedback semiconductor laser and its manufacture | |
JP6928824B2 (en) | Optical waveguide structure | |
JP2842387B2 (en) | Manufacturing method of semiconductor optical integrated device | |
JP3159914B2 (en) | Selectively grown waveguide type optical control element and method of manufacturing the same | |
JP6782082B2 (en) | Semiconductor optical devices and their manufacturing methods | |
JP4005519B2 (en) | Semiconductor optical device and manufacturing method thereof | |
KR20220032220A (en) | tunable laser diode | |
JPH07335977A (en) | Semiconductor laser and optical integrated device and manufacture thereof | |
JPS61212082A (en) | Integrated semiconductor laser | |
JPH1022567A (en) | Distribution feedback type semiconductor laser and its manufacture | |
JPH10270789A (en) | Semiconductor optical device used for optical communication and its manufacturing method | |
JPH08279648A (en) | Manufacture of distributed feedback semiconductor laser device |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: FURUKAWA ELECTRIC CO., LTD., JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HIGA, YASUTAKA;KAWAKITA, YASUMASA;SIGNING DATES FROM 20190712 TO 20190718;REEL/FRAME:049969/0658 |
|
FEPP | Fee payment procedure |
Free format text: ENTITY STATUS SET TO UNDISCOUNTED (ORIGINAL EVENT CODE: BIG.); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: APPLICATION DISPATCHED FROM PREEXAM, NOT YET DOCKETED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: FINAL REJECTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE AFTER FINAL ACTION FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: ADVISORY ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NOTICE OF ALLOWANCE MAILED -- APPLICATION RECEIVED IN OFFICE OF PUBLICATIONS |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: AWAITING TC RESP, ISSUE FEE PAYMENT VERIFIED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: PUBLICATIONS -- ISSUE FEE PAYMENT VERIFIED |
|
STCF | Information on status: patent grant |
Free format text: PATENTED CASE |